Fuel injection arrangement



y 1959 L. STEINKE FUEL. INJECTION ARRANGEMENT Filed Oct. 28, 1957 (Wllf ni d St s Patent 2,886,015 FUEL INJECTION ARRANGEMENT Leo Steinke, Stuttgart, Germany, assignor to Robert Bosch G.m.b.H., Stuttgart, Germany Application October 28, 1957, Serial No. 692,849

. Claims priority, application Germany October 26, 1956 14 Claims. (Cl. 123-32) known arrangements of this type the valve is' a normally closed one and is opened uponenergization, andsuch energization is brought about automatically by a switch device which is synchronized with the operation of the engine. In such arrangements there arises the problem 2 termined minimum voltage, the power branch being in circuit with the source of electrical energy and with the valve means; voltage supplying means for impressing across the control branch at a predetermined instant during a cycle of operation of the engine a voltage greater than the minimum voltage, the voltage supplying means being so constructed and arranged that the duration of the impression of voltage is shorter than the time interval throughout which the valve means is to be maintained in its open position; and a resistor-capacitor timedelay circuit connected across the control branch and adapted to be charged by the voltage supplying means during the impression of voltage across the control branch to a voltage greater than the minimum voltage for maintaining the voltage across the control branch above the minimum voltage for a predetermined time interval following the cessation of the impression of voltage by the voltage supplying means. i l l l The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific of providing suitable means for controlling the duration of fuel injection, i.e., of providing suitable means for maintaining the valve open the required lengthof time depending upon the conditions under which the engine is operated, such as high speed, low speed, full load, partial load, etc. able diinculties arose in converting the variousrequired time lengths into electrical quantities which control the operation of the valve that regulates thefuel supply to the engine. l l it It is therefore an object of the presentinvention to provide a fuel injectionarrangement which overcomes the above disadvantages.

Experience has shown that considerterval during which fuel is injected is easily controlled.

clude the provision of a fuel injection arrangement which may readily be built into existing constructions.

With the above objects in view, the present invention mainly consists in a fuel injection arrangement for an internal combustion engine which comprises valve means i forcontrolling the flow of fuelto theengine and means I which are operatively associated 'withthe engine and with 'the valve means for opening the latter at a predetermined instantduring a cycle of operation of the engine and for closing the valve means after the elapse ofta time interval 3 'the duration of which is predeterminable independently of the instant at which the valve means are opened. n

More particularly, the preeent invention comprises electricallyoperated'valverneansfor controlling the flow of fuel to the engine the construction of the valve jmeans 'beingsuch thatwhen itisunenergized it occupies its :1 closed position' an d that when his energizedrit occupies its open position; a source of electrical energy; an electron the control branch is electrically biased above a predeembodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a schematic diagram of a fuelinjection arrangement according to the present invention; and

Fig. 2 is a voltage-time graph illustrating the operation of the circuit shown in Fig. 1. l

Referring now to the drawings, and to Fig.1 thereof in particular, there is shown a fuel injection arrangement which incorporates an electrically operated valve V. The latter controls the flow of fuel from a supply conduitL to a connecting conduit 0 which communicates withthe internal combusion engine (not shown). The valve is of the electro-magnetic type and includes a winding M which attracts a valve plunger P. The latter is continuously urged downwardly, as viewedin Fig. l, to its closed position by a suitable bias spring (not' shown) but is raised to its open position upon energization of the coil M. Thus, the valve V is one which when une'nergized occupies its closed position and when energized occupies its open position.

The winding M is connected in circuit with the collector Kjand the emitter E of a transistor T,;as well as with a source of electrical energy G, the latter normally being the battery or other D.C. source which is usually associated with an internal combustion engine. The base of the transistor is indicated at B, the connection of the transistor being of the common-emitter type so thatjthe collector-emitter circuit constitutes thepower branch of the transistor and the base emitter the control branch. As is well known in the art, the transistor is an electron flow control device which is conductivejonly when a certain minimum electrical bias is impressed across the control, branch. This means that electrons may flow through the power branch of the transistor only when a voltage greater than the required minimumvoltage is impressed across the control branch. In practice, the transistor may be a 2N 173. j n j j The base B of the transistor T is connected to the sourceof electrical energyG by way of a time delay switch D and an additional switch S. The latter has a stationary contact b and a movable contact a whichijcan be moved to closed position by a rotating cam N which n i is suitably coupled to the crankshaft of the engine (not shown) so that the switch S is periodically actuated by and operates in synchronism with the engine. .IflythlS jway, theswitch S will, during successive cyclespf .operation of the engine, always be closed at thesame preter is such that when the switch S is closed, the winding is energized by the source G and the switch D opened. The "switch D is so constructed andarranged that there is a 'briefdelay between the instant the winding W is energized and the instant that the arm e is actually moved out ofengagernent with the stationary contact d. This time delay, the significance of which will be described below, is of the order of several milliseconds.

Additionally, a resistor-capacitor time delay circuit Z is connected across the control branch of the transistor, -i.e., across the base B and the emitter E. The time delay circuit includes a capacitor C, a variable charging re- 'sistor-R ,and a variable discharge resistor R The operation of the above'described fuel injection arrangement is as follows:

The cam N closes the switch at the start of the work "stroke of the engine. As a result, the control branch of 'the transistor T, the time delay circuit Z, and the winding W of the time delay switch D are connected across the'source G, and this causes the following:

(1) With the voltage of the source G being greater than the minimum voltage required to render the transistor conductive, a sufficiently high voltage is impressed across the control branch to render the transistor conductive (the transistor having been left non-conductive at the end of the previous cycle of operation). This, in turn; permits a current to fiow through the power branch so that the winding M of the valve V is energized, there- Elby raising the plunger P and opening the valve V. It will :beapparent that the valve V' will be maintained in its open position only so long as the electrical biasacross .lthe'controlbranch of the transistor is suflicient to permit :enough current to flow through the power branch as will adequately energize the winding M. For purposes of -eXplanation, it will be assumed that the winding M is -sufliciently energized to hold the plunger P in its open position so long as the transistor T is conductive.

(2) A charging voltage is applied to the capacitor C of the time delay circuit Z.

(3) The winding W of the time delay switch D is energized.

The above-described three events occur simultaneously. As set forth above, there is a brief time delay between .the instant of energization of the winding W and theacvtual opening of the switch S, and the capacitance of the capacitor C and the resistances of the resistors R and R .are such that the time delay is suflicient for the capacitor C to be charged to a voltage which is higher than the minimum voltage required to maintain the transistor T -in conductive state. Consequently, by the time the contact arm e of the switch D is actually moved out of engagement with the stationary contact a, the voltage U across the capacitor C which, upon opening of the switch D, is the voltage U impressed across the control branch of the transistor, will be sufiicient to maintain the transistor conductive so that current will continue to flow through the power branch thereby maintaining the valve V in its open position.

As soon as the switch D is opened, the capacitor C will commence to discharge by way of a parallel circuit one branch of which is constituted by the resistor R and the other branch of' which is constituted by the series "circuit formed by the resistor R and the emitter-to-base resistance of the transistor (the resistor R being of no consequence). As soon as the capacitor has discharged to a point at which U is less than the voltage required to'render the transistor conductive, no further current can flow through the winding M and the valve V assumes 'its closed position. Thus, the valve will have remained open for a certain predetermined interval following the initial closing of the switch S, it being apparent that the length of this interval can be regulated by varying the resistances of the resistors R and/or R Fig. 2 is a graphical representation of the voltage-time relationships between the various circuit components, it being assumed that the effect of the resistor R is negligible.

The solid horizontal line t represents the time during which the switch S is closed, and it will be seen that the initial closure of this switch occurs at the instant t the exact time at which the switch thereafter opens under the influence of the cam N being of no particular interest, suifice it to say that the switch remains closed throughout a fraction of each cycle of operation but for a period not less than the brief time interval required for the switch D to open after energization of the winding W.

The time during which the switch D is closed is represented by the solid horizontal line 13 This switchwhich will, during the previous cycle, have assumed its closed position as-soon as the cam N permits the switch S to open-is still closed at the instant t and will not, due to its inherent time delay indicated by the bracket 1 open until the instant t In practice, the time delay will be approximately 5 milliseconds, and during this time interval t the voltage U i.e., the voltage impressed across thecontrol branch of the transistor, is equal to the voltage U which is the voltage of the source G and is of the order of 12 volts. Also, during this time in terval t the capacitor C will be charged by the source G, and the voltage U across the capacitor will increase substantially linearly, as indicated by the dotted line 7']:- With the capacitance of the capacitor C being microfarads and. the resistance of the resistor R being 50 ohms, the resistor-capacitor circuit R C has a charging time constant of 5 milliseconds and the capacitor will, during the time interval t;,, be charged to a voltage U Upon opening of the time delay switch D at the-instant t the control branch of the transistor as well as the time delay circuit Z are disconnected from the source G, and the only voltage whichappears across the control branch is the voltage U across the capacitor. Of course, this voltage immediately begins to drop since the capacitor C commences to discharge by way of the resistor R as well as by way of a parallel branch constituted by the resistor'R and the emitter-to-base resistance of the transistor (the resistance of the resistorR being considered negligible). With the resistance of resistor R being about 'ohms, the discharge time constant is about 10 milliseconds, this time constant being indicated by the line 1- As soon as the voltage U which is the same as the voltage U appearing across the control branch of the transistor, drops to the voltage U at which the transistor ceases to be conductive, no more current will flow through the power branch. This occurs at the instant shown at t at which time the valve V assumes its closed position. Thus, the total time during which the valve V is open is the time interval indicated by the bracket t The time interval during which the valve remains open may be increased by decreasing the resistance of resistor R This decreases the charging time constant as indicated by theline 1- the slope of which is steeper than that of line TI- Inasmuch as the charging time of the capacitor remains constant, this factor being determined solely by the inherent time delay of the time delay switch D, the voltage to which the capacitor will be charged is increased so that at the instant t the voltage U is equal to U which is .higher than U With the discharge time constant r yremaining unchanged, the voltage U will not'drop toU until t so that the valve V is retained in its open'position for a period of time longer than before.

Additionally or alternatively, the time interval during which the valve remains open may be increased'by-"in' creasing the resistance of the resistor R Thisincreases the discharge time constant as indicated by line 1- so that the voltage .U,, will not drop to U until t Thus, the time interval throughout which the valve V remains open subsequent to theclosing of the switch S,

and consequently the amount of fuel supplied into the engine, may be regulated within very wide limits independently of the instant at which fuel injection commences.

According to the present invention the time regulation may be accomplished automatically by providing a device for periodically short-circuiting the capacitor C, or for periodically connecting an additional resistor R across the capacitor, thereby decreasing the discharge time thereof. Such a device includes a periodically-actuated switch Q which is also operated in synchronism with the engine and which may, if desired, be operated at a frequency which is a multiple of the frequency at which the switch S is operated. Thus, the discharge time of the capacitor, and consequently the time interval during biasing means during the impression of bias across said control branch to a bias greaterthan said minimum bias for maintaining the bias across said control branch above said minimum bias for a predetermined time interval following thecessation of the impression of bias by said biasing means.

2. In a fuel injection arrangement for an internal combustion engine, in combination, electrically operated valve means for controlling the flow of fuel to the internal combustion engine, said valve. means when unenergized occupying its closed position and when energized occupying its open position; a source of electrical energy; an electron flow control device having a control branch and a power branch through which electrons may flow only when said control branch is electrically biased above a predetermined. minimum voltage, said power branch being in circuit with said source of electrical energy and with said valve means; a resistor-capacitor time delay, circuit connected across said control branch;

and means connected in parallel with said control branch and with said time delay circuit for impressing thereacross at a predetermined instant during a cycle of operation of the engine a voltage which is greater than said a toggle switch which is continuously biased into one position and a secondtransistor may be used. It is also possible to control the voltage to which the capacitor is charged by using as the source of electric energy G a generator which is coupled to the engine so that the output of the generator increases upon increased rotational.

speed. j.

It will be understood that each of the elements described above,- or two or more together, may also find a useful application in other types of control arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in a fuel injector arrangement for an internal combustion engine, it is not intended to be limited to the details shown, since various modifications and strucreveal the gist of the present invention that others can by applying current knowledge readily adapt it for various 'tural changes may be made without departing "in any applications without omitting features that, from the j standpointof prior art, fairly constitute. essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations. should and are .intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed-as new and desired to be secured by Letters Patent is: i i

1. In a fuel injection arrangement for an internal combustion engi ne, in' combination, electrically operated valve bustion engine, said valve means when unenergized occupying its closed position and when energized occupying its open position; a source of electrical energy; an electron flow control device having a control branch and a power branch through which electrons may flow only when said control branch is electrically biased above a predetermined minimum bias, said power branch being in circuit with said source of electrical energy and with said valve means; biasing means for impressing across said control branch at a predetermined instant during a cycle of operation of the engine a bias greater than said minimum bias, said biasing means being so constructed and arranged that the duration of the impression of bias is shorter than the time interval throughout which said valve means is to be maintained in its open position; and a resistor-capacitor time delay circuit connected across minimum voltage, said last-mentioned means being so constructed and arranged that the duration of the impression of voltage is shorter than the time interval throughout which said valve means is to be maintained in its open position, whereby said time delay circuit is charged to a voltage higher than said minimum voltage and maintains the voltage across said control branch above said minimum voltage for a predetermined time interval following the cessation of the charging of said time delay circuit.

. 3. In a fuel injection arrangement for an internal combustion engine, in combination, electrically operated valve means for controlling the flow of fuel to the internal combustion engine, said valve means when unenergized occupying its closed position and when energized occupying its open position; a source of electrical energy; a transistor having a control branch and a power branch,

the latter being in circuit with said source of electrical energy and with said valve means; voltage supplying means operatively associated with the engine and in circuit with said control branch of said transistor for impressing thereacross at a predetermined instant during a cycle of operation of the engine a voltage greater than that which is required to render said transistor conductive; and a resistor-capacitor time delay circuit connected across said control branch of said transistor and adapted to be charged by said voltage supplying means, while the latter impresses, a voltage across said control branch,

to a voltage greater than said voltage which. is required to render said transistor conductive, whereby said transistorrernains conductive for a predetermined time interval following the cessation of the impression of voltageby said voltage supplying means. i

4. In a fuel injection arrangement for an. internal combustion engine, in combination, electrically operated during a cycle of operation of the engine, a voltage greater than that which is required to render said transistor conductive, said voltage supplying means being so constructed and arranged that the duration of the impression of voltage is shorter than the time interval throughout which, in said cycle, said valve means is to be I assaois maintained in its open position; and ,a resistor-capacitor time delay circuit connected across said control branch of said transistor and adapted to be charged by said voltagesupplying means, while the latter impresses a voltage across said control branch, to a voltage greater than said voltage which is required to render said transistor conductive, whereby said transistor remains conductive for a predetermined time interval following the cessation of the impression of voltage by said voltage supplying means and said valve means is maintained in its open position until the charge on said time delay circuit has dropped to a value at which the voltage across said control branch is below said voltage which is required to render said transistor conductive.

5. The combination defined in claim 4 wherein said time delay circuit includes a resistor and a capacitor in Series-circuit connection.

6. The combination defined in claim 4 wherein said time delay circuit includes a resistor and a capacitor in parallel-circuit connection.

7. The combination defined in claim 4 wherein said time delay circuit includes a capacitor, a first resistor in series-circuit connection with said capacitor, and a second resistor in parallel-circuit connection with said capacitor.

8. The combination defined in claim 6 wherein said resistors are variable resistors.

9. The combination defined in claim 4 wherein said time delay circuit includes means connected across the capacitor for periodically short-circuiting the same, whereby the discharge time of said time delay means, and

consequently the time interval during which said valve means is maintained in its open position, is diminished.

10. The combination defined in claim 4 wherein said time delay circuit includes means connected across the capacitor for periodically connecting an additional resistor thereacross, whereby the discharge time of said time delay means, and consequently the time interval during which said valve means is maintained in its open position, is diminished.

11. The combination defined in claim 3 wherein said voltage supplying means include a time delay switch connected in circuit with the parallel circuit constituted by said control branch of said transistor and said resistorcapacitor time delay circuit, said time delay switch being normally closed and having an electrically energizable actuator, said time delay switch being so constructed and arranged that when said actuator thereof is energized,

said switch assumes its open position a predetermined time interval thereof, said voltage supplying means further including an additional switch which is connected in circuit with the series-parallel circuit constituted by said control branch of said transistor, said time delay circuit and said time delay switch and which is also connected in circuit with said actuator of said time delay switch for electrically connecting said series-parallel circuit as well as said actuator of said time delay switch, at said predetermined instant during a cycle of operation of the engine, to a source of electrical energy, whereby said seri s-pa a l c uit is e ect i y conne e to the so of le ical ener y or the d r ti of s i P determined time interval of said time delay switch.

12. The combination defined in claim 3,wherei r 1 said voltage supplying means include a timedelay switch connected in circuit with the parallel circuit constituted by said control branch of said transistor and said resistorcapacitor time delay circuit, said time delay switch being normally closed and having an electrically energizable actuator, said time delay switch being so constructed and arranged that when said actuator thereof is energized, said switch assumes its open position a predetermined time interval thereof, said voltage supplying means further including an additional switch which is connected in circuit with the series-parallel circuit constituted by said control branch of said transistor, said time delay circuit and said time delay switch and which is also connected in circuit with said actuator of said time delay switch for electrically connecting said series-parallel circuit as well as said actuator of said time delay switch, at said predetermined instant during a cycle of operation of the engine, to said source of electrical energy, whereby said series-parallel circuit is electrically connected to said source of electrical energy for the duration of said predetermined time interval of said time delay switch.

13. The combination defined in claim 12, and means for periodically closing said additional switch at said predetermined instants of successive cycles of operation of the engine.

14. In a fuel injection arrangement for an internal combustion engine, in combination, an electrically operated valve means for controlling the flow of fuel to the internal combustion engine, said valve means when unenergized occupying its closed position and when energized occupying its open position; a source of electrical energy; a transistor having a base, an emitter and a collector, said emitter and collector being in circuit with said source of electrical energy and with said valve means; voltage supplying means operatively associated with the engine and in circuit with said base and emitter of said transistor for impressing thereacross, at a predetermined instant during a cycle of operation of the engine, a voltage greater than that which is required to render said transistor conductive; and a resistor-capacitor time delay circuit connected across said base and emitter of said transistor and adapted to be charged by said voltage supplying means, while the latter impresses a voltage across said base and emitter, to a voltage greater than said voltage which .is required to render said transistor conductive, whereby said transistor remains conductive for a predetermined time interval fol- References Cited in the file of this patent UNITED STATES PATENTS Barclay Sept. 24, 1957 Pribble Dec. 3, 1957 

